How to change Text property of a TextBlock in WP7 and WP8?

Question

I'm a beginner in WP8.
I have a problem...
For Example:
I have 2 pages in my windows phone application, and on first page I have 3 buttons and on second page I have a TextBlock control.
How can I change its text property on the second page by clicking the buttons which are on the first page?

I only know how to change text when the controls are on the same page:

private void button1_Click(object sender, RoutedEventArgs e)
{
    textBlock1.Text= "Hello!";
}

Answer 1

This seems to me like bad practice, but it can be done by getting and storing instance of the page with the textblock in a global variable and accessing the textblock from that instance.eg

public Page myFirstPage = null;

public partial class FirstPage : Page
  {
     FirstPage()
      {
           initializeComponent(); 
      } 

     void onLoadedEvent(Object Sender, Eventargs e)
     {
        myFirstPage = this;
     }
  }

Then you can access every thing in any other page by doing this

myFirstPage.TextBlock1 = "FooBar";

Answer 2

You can address this problem in MVVM way. Have a proper viewmodel to store your data :

public class MyViewModel
{
    public String WelcomeText { get; set; }
}

Declare property of type above viewmodel in App.xaml.cs , so that you can share same data across application pages :

public MyViewModel MyViewModel = new MyViewModel();

Set DataContext of both pages to the same viewmodel :

public Page1()
{
    InitializeComponents();
    this.DataContext = App.MyViewModel;
}

public Page2()
{
    InitializeComponents();
    this.DataContext = App.MyViewModel;
}

Data-bind textblock in page 2 :

<TextBlock Text="{Binding WelcomeText}"/>

Then in button click event handler of page 1, simply update the viewmodel property :

private void button1_Click(object sender, RoutedEventArgs e)
{
    App.MyViewModel.WelcomeText= "Hello!";
}